Now Playing: Georgetown athlete walks for 1st time since suffering spinal-cord injury
Now Playing: Man confined to wheelchair after spinal injury walks at college graduation
Now Playing: New study shows alarmingly low rates of metabolic health
Now Playing: Recall involving blood pressure medications expanding
Now Playing: Baby ibuprofen recalled from Walmart, CVS, Family Dollar
Now Playing: 1st baby born using uterus transplanted from deceased donor
Now Playing: More US beef being recalled over salmonella fears
Now Playing: The best toys for kids make use of their imaginations, not a screen
Now Playing: Two blood pressure medications pulled in heart-drug recall
Now Playing: Younger school entry linked to ADHD diagnosis: Study
Now Playing: Teen left in tears as her classmates reveal she’s cancer free
Now Playing: Studies show women who snore pose greater cardiac risk
Now Playing: US life expectancy drops for 3rd year in a row
Now Playing: Deborah Norville of ‘Inside Edition’ shares how she dropped 30 pounds
Now Playing: Doctor behind first genetically modified babies: ‘I feel proud’
Now Playing: Researcher in middle of gene controversy defends his work
Now Playing: Number of cases of AFM nearly doubled in the last month: CDC
Now Playing: Romaine lettuce from California linked to E. coli, FDA says
Now Playing: How to use fats and oils for healthy hair, skin
Now Playing: New cancer treatment credited for saving the life of 9-year-old boy